A New Echo-Doppler Method of Assessing Pulmonary Arterial Wave Reflection: In Vivo Validation

Background: Pulmonary arterial (PA) wave reflection provides additional information for assessing right ventricular afterload, but its applications is hampered by the need for invasive pressure and flow measurements. We tested the hypothesis that PA pressure and flow waveforms estimated by Doppler echocardiography could be used to quantify PA wave reflection. Methods: Doppler echocardiographic images of tricuspid regurgitation and right ventricular outflow tract flow used to estimate PA pressure and flow waveforms were acquired simultaneously with direct measurements with a dual sensor-tipped catheter under various hemodynamic conditions in a canine model of pulmonary hypertension (n=8). Wave separation analysis was performed on echo-Doppler derived as well as catheter derived waveforms to separate PA pressure into forward (Pf) and backward (Pb) pressures and derive wave reflection coefficient (RC) defined as Pb divided by Pf.Results: RC by echo-Doppler agreed well with RC indices by catheter (RC: bias = 0.13, 95% limits of agreement = -0.25 to 0.26). RC correlated negatively with pulmonary arterial compliance and right ventricular systolic function. Conclusions: This echo-Doppler method yields accurate measurement of reflected wave in the pulmonary circulation, paving the way to a more integrative assessment of pulmonary hemodynamics in the clinical setting.

Effects of cardiac pacemakers on left ventricular volumes and function assessed by 3D echocardiography, Doppler method, and global longitudinal strain

Background Many previous studies reported the negative effects of right ventricular (RV) pacing on the left ventricular (LV) structure and ejection fraction. Studying pacing hemodynamics is essential to understand these detrimental effects. In this study, we tried to understand RV pacing effects on LV volumes and function using advanced tools like 3D echo and global longitudinal strain (GLS). This was a prospective study of 175 consecutive patients (LVEF>50%) presented permanent pacing. Of 175 patients, only 50 patients met study criteria, divided into two groups (single or dual pacing). LV volumes and function were assessed by full-volume 3D echocardiography and GLS before pacing, at 1-week and 6-month post-pacing. Cardiac output (COP) was calculated by pulsed wave Doppler method and 3D echo. Results Doppler method results were similar to 3D echo in calculating SV and COP. At 1-week post pacing, both groups showed a significant decrease in SV due to a drop in EDV while ESV did not change significantly. Despite the drop in SV, there was a significant increase in cardiac output (COP) due to achieving higher heart rates post-pacing. There was a significant drop in EF and GLS in both groups. At 6 months, SV continued to decrease with a corresponding decrease in COP and LVEF. This drop in SV was due to a significant increase in ESV while EDV did not show a significant change at a 6-month follow-up. Also, the drop EF and GLS became more significant. There were no significant differences between both groups regarding the changes in LV volumes (EDV, ESV, SV), LVEF or GLS throughout the study (pre-pacing, at 1-week and 6-months post pacing). However, dual-chamber pacing group provided higher heart rates and as a result higher COP than the single-chamber group. Conclusions RV pacing led to a significant drop in LV COP, ejection fraction (EF), and GLS over short- and long-term duration. Dual chamber pacing provided higher COP than a single chamber pacing. This was due to tracking the S. A node with pacing at higher heart rates not due to an increase in SV and preserving atrioventricular synchrony. Both Doppler method and 3D echo can be used to calculate SV and COP.

Granular Fertilizer Mass Flow Measurement and Vehicle Experiments Based on Microwave Doppler Method

HighlightsA microwave Doppler-based fertilizer mass flow measurement system was developed.The measurement system was applied in vehicle experiments.Power spectra of mass flow signal and vibration signal were obtained and analyzed.Interference suppression algorithm based on CA-CFAR reduced vibration interference.Fertilizer mass flow measurement accuracy was improved by interference suppression.Abstract. The fertilizer mass flow measurement system is typically installed on the fertilizer applicator. However, vehicle vibrations are inevitable during field operation of fertilizing equipment, and can interfere with mass flow signals, thereby affecting the accuracy of mass flow measurements. In this article, a mass flow measurement system based on the microwave Doppler method was introduced. The dominant frequency (fdot) related to fertilizer velocity and the power spectral density (PSD) related to fertilizer concentration were obtained from the Doppler signal of the granular fertilizer processed using fast Fourier transform. The product of fdot and PSD is defined as the sensor output value (SOV). The relationship between SOV, PSD, and fertilizer mass flow (FMF) was studied under vehicle conditions. The linear regression models of 22-8-10 (MOP) high-nitrogen poly-?-glutamic acid fertilizer were established using the least squares method, and the vibration signals were measured. Based on analysis of the power spectra of the mass flow and vibration signals, an interference suppression algorithm based on cell average constant false alarm rate (CA-CFAR) was presented to reduce vibration interference. To verify the performance of the novel vibration interference reduction algorithm, vehicle experiments were conducted at different tractor velocities. The results show that mass flow measurements ranged from 1300 to 3000 g min-1. It was found that using only the PSD related to concentration for flow measurement gave better measurement accuracy compared with SOV, and relative errors of the system were within 8.1%. Correlation between the PSD and FMF improved with interference suppression algorithm based on CA-CFAR. The determination coefficient increased from 0.01 to 0.92, 0.97 to 0.99, and 0.96 to 0.98 at three different tractor velocities, respectively. From the results, it was evident that the algorithm effectively eliminated vibration interference signals in vehicle conditions. In future work, the conditions of the soil will be considered and the performance of the mass flow measurement system will be tested in the field. Keywords: Fertilizer mass flow, Microwave Doppler radar, Tractor vibration, Vehicle experiment, Vibration interference suppression.

Comparative study between effects of single and dual chamber pacemaker on stroke volume, cardiac output and strain using 3D echocardiography, pulsed Doppler method and global longitudinal strain (GLS)

Background Dual-chamber cardiac pacing is thought to deliver higher clinical benefits as compared with single-chamber ventricular pacing. During the last two decades, 3D-echocardiography developed from a sophisticated, time-consuming method preferably used as a scientific tool towards a routine clinical approach. At present, available evidence suggested that 3D echocardiography provided improved accuracy and reproducibility over 2D methods for LV volume and function calculation. It was also more useful for early detection of volumetric changes associated with changes in cardiac hemodynamics. Methods This was an observational study of fifty consecutive patients without structural heart disease and preserved ejection fraction (EF>50%) presented with high grade atrioventricular block for permanent pacemaker implantation. They were assigned to receive a single-chamber ventricular pacemaker (23patients) or a dual-chamber pacemaker (27 patients). Stroke volume and cardiac output was assessed by full volume 3D echo and pulsed wave Doppler before implantation, at one-week and 6-months after implantation. For the Doppler method, LVOT diameter was measured for each patient at baseline and same value was used at follow up to avoid any confounding factors. GLS was measured at all visits. Results At one-week post pacing, both groups showed a significant decrease in SV due to a drop in EDV while ESV did not change significantly. There was a significant increase in cardiac output (COP) more in dual-chamber pacing group than in the group with single-chamber pacing. However, there were no significant differences between both groups regarding stroke volume (SV), end-systolic volume (ESV), end-diastolic volume (EDV) or ejection fraction (EF) during all time intervals (pre-pacing, at one-week and 6-months post pacing). GLS showed equal decrease in both groups. At 6 months, SV continued to decrease, and COP showed significant decrease. This drop in SV and COP was due to a significant increase in ESV while EDV did not show significant change at 6-month follow up. There was no significant difference between full volume 3D and Doppler methods regarding SV and COP values at all time intervals in both groups. GLS showed additional equal decrease in both groups. Conclusion Dual chamber pacing provided higher COP than single chamber pacing. This is due to pacing at higher heart rates, not due to increase in SV by maintaining atrioventricular synchrony. It was shown in both experimental and clinical studies that RV pacing leads to ventricular dyssynchrony, similar to that of left bundle branch block with subsequent electrical, mechanical and anatomical changes leading to detrimental effects on left ventricular structure and function. Both groups showed significant drop in GLS plus SV, COP and EF at 6-months due to significant increase in ESV. 2D echocardiography and Doppler method were not inferior to 3D echocardiography regarding calculation of SV and COP. Haemodynamics of single & dual pacing Funding Acknowledgement Type of funding source: None